1. Field of the Invention
The present invention relates to a fan control system, and particularly to a fan control system using a microcontroller.
2. Description of the Related Art
Generally, conventional fan control systems are constructed with various electrical circuits or elements in order to achieve control. Examples of the conventional fan control system with different functions are described hereafter in detail with reference to FIG. 1a, FIG. 1b, FIG. 1c, FIG. 2a and FIG. 2b. 
A general function of the conventional fan control system is the fan rotation speed control. FIG. 1a shows an example of the conventional fan control system, in which an external variable DC voltage is applied for fan rotation speed control. In FIG. 1a, the fan 500 receives an operating voltage Vcc, and determines a pulse width modulation (PWM) signal with a comparator 520. The comparator 520 receives the external variable 0xcx9c5V DC voltage and a triangular wave and determines the PWM signal, then outputs the PWM signal via a switch 590 to the fan-driving circuit (FDC) 510 in order to determine the rotation speed of the fan motor.
Another example of the conventional fan rotation speed control is shown in FIG. 1b, in which a temperature-sensitive resistor (or a thermistor) 530 is applied to determine the variable voltage. In FIG. 1b, the fan 500 receives an operating voltage Vcc, and determines a pulse width modulation (PWM) signal with a comparator 520. The comparator 520 receives a triangular wave and a variable voltage obtained from the operating voltage Vcc with a voltage dividing process performed by the temperature-sensitive resistor 530 and a fixed resistor 540. Thus, the comparator 520 determines the PWM signal, then outputs the PWM signal via a switch 590 to the fan-driving circuit (FDC) 510 in order to determine the rotation speed of the fan motor.
A further example of the conventional fan rotation speed control is shown in FIG. 1c, in which the input signal for controlling the fan 500 is an external PWM signal, shown as PWM(external) in FIG. 1c, instead of a voltage. In FIG. 1c, the fan 500 receives an operating voltage Vcc. Meanwhile, the external PWM signal PWM(external) passes through a certain circuit, such as a resistor 542, to be transformed to an internal PWM signal PWM(internal). The internal PWM signal is then output to the fan-driving circuit (FDC) 510 via a switch 590 in order to determine the rotation speed of the fan motor.
In addition to the fan rotation speed control, the conventional fan control system can achieve slow startup (soft startup) or any other specific rotation speed detection by position control of the fan motor rotor. An example of this is shown in FIG. 2a, in which the fan motor is driven by a fan-driving IC (FDIC) 510. In FIG. 2a, the fan 500 receives an operating voltage Vcc. Meanwhile, the FDIC 510 controls the coils 570 of the fan motor and incorporates with, the magnetic induction component such as a Hall element 560, and other components such as the capacitor 550 to control the rotor position of the fan motor, so that the required slow startup (soft startup) or any other specific rotation speed detection can be achieved.
FIG. 2b shows another method to achieve the above-mentioned rotor position control of the fan motor. In FIG. 2b, a Hall element 560 and a plurality of resistors 544, 546 are applied to control the coils 570 of the fan motor to drive the fan motor, so that the required slow startup (soft startup) or any other specific rotation speed detection can be achieved.
In the conventional fan control system for performing the fan rotation speed control, however, the input voltage and the coils of the fan motor determine the rotation speed of the fan motor. That is, a relationship between the rotation speed and the input voltage exists as shown in the diagram of FIG. 3 when the coils of the fan motor are fixed. In FIG. 3, this relationship is shown in a function F, corresponding to the fixed coils. If an input voltage Vo is applied, the function F determines the rotation speed according to the input voltage Vo at point A, in which a first rotation speed Wo is obtained. As a result, if the input voltage is kept constant, the only way to obtain a variable rotation speed is to provide several sets of coils of the fan motor, in which each set of coils corresponds to a different function F. This increases the size and manufacturing cost of the fan.
Further, in the conventional examples shown in FIG. 1a and FIG. 1b, the comparator 520 is applied to obtain the PWM signal. However, in these examples, the input voltage is generated by hardware-type components which are hard to be replaced, which increases the possibility of error between the PWM signals and the triangular wave signal, so that the rotation speed control is not stable.
Further, in the conventional example shown in FIG. 1c, the frequency and power of the internal PWM signal are limited to those of the external PWM signal. If the external PWM signal has a low frequency, the vibration due to the low frequency signal increases, a disadvantage to the fan properties and lifetime. On the other hand, if the external PWM signal has a high frequency, the circuit reaction time is relatively shortened, which can lead to unstable rotation speed. Further, in the transformation of the PWM signal, the frequency of the PWM signal can reach an audible frequency. In this case, annoying noise occurs in the fan motor.
Further, in the conventional examples shown in FIG. 2a or FIG. 2b, the fan control system is constructed by fixed hardware-type components with fixed properties. Thus, the position control of the fan motor rotor is restricted by the properties of the components.
As shown in FIG. 3, the relationship between the rotation speed and the operating voltage of the fan motor has a linear function (F). Further, the fan motor has a limitation of an endurable maximum rotation speed Wmax, as shown in FIG. 3. In the conventional fan control system, a maximum input voltage Vmax can be obtained according to the maximum rotation speed Wmax at point B. That is, the input voltage V is limited to the maximum input voltage Vmax in order to prevent overheating of the fan motor. Generally, a typical fan motor has a maximum input voltage Vmax of 60V. However, in a conventional fan control system, additional voltage transformers or voltage dividers are required if the power supply available for the input voltage exceeds this maximum input voltage Vmax. This not only increases the size and manufacturing cost of the fan control system, but also increases instability of the input voltage resulting from the voltage dividing process.
Further, the conventional fan control system can be modified to provide protection from overheating or exceeding allowable rotation speeds. In this case, however, additional components are required, which also leads to increased the size and manufacturing cost of the fan control system.
In view of this, the present invention discloses a fan control system, in which a microcontroller is applied in order to solve the conventional problems.
The present invention discloses a fan control system, which has a programmable microcontroller to receive an input signal, determining an output signal according to the input signal, and outputting the output signal; and a fan-driving unit to receive the output signal and adjust a rotation speed for driving the fan motor according to the output signal.
In the above-mentioned fan control system, the fan-driving unit can be a fan-driving circuit. Further, the input signal can be a variable voltage signal, an external pulse width modulation (PWM) signal, or a rotation speed signal obtained by detecting the actual rotation speed of the fan motor, and the output signal can be a PWM signal. Further, the microcontroller may be programmed to output an alarm when the rotation speed signal is different from a preset value stored in the microcontroller.
The present invention further discloses another form of a fan control system, in which a fan-driving microcontroller receives an input signal, determines an output signal according to the input signal, and adjusts a rotation speed for driving the fan motor according to the output signal.
In the above-mentioned fan control system, the input signal can be a variable voltage signal, an external pulse width modulation (PWM) signal, or a rotation speed signal obtained by detecting the actual rotation speed of the fan motor, and the output signal can be a PWM signal. Further, the microcontroller may be programmed to output an alarm when the rotation speed signal is different from a preset value. The above-mentioned fan control system may further have a magnetic induction component, such as a Hall element, for detecting the magnetic field phase of the fan motor in order to output the input signal to the fan-driving microcontroller.
The present invention further discloses another form of a fan control system, in which the fan motor is operated normally at not greater than a preset maximum rotation speed. The fan control system has a programmable microcontroller to receive an input voltage and a rotation speed signal obtained by detecting the actual rotation speed of the fan motor, determining an output signal according to the input voltage and the rotation speed signal, and outputting the output signal; and a fan-driving unit to receive the output signal and adjust the rotation speed for driving the fan motor according to the output signal. When the rotation speed is lower than a first rotation speed, the rotation speed is in a relation of a first function to the input voltage; when the rotation speed is greater than the first rotation speed, the rotation speed is in a relation of a second function to the input voltage; and a first maximum voltage corresponding to the maximum rotation speed in the relation of the first function is lower than a second maximum voltage corresponding to the maximum rotation speed in the relation of the second function.
In the above-mentioned fan control system, the fan-driving unit can be a fan-driving circuit, and the input signal can be a variable voltage signal. Further, the microcontroller may be programmed to output an alarm when the rotation speed signal exceeds a second rotation speed. It is preferable that the first function and the second function are linear functions, and the second function has a slope lower than that of the first function.
The present invention further discloses a further form of control, in which the fan motor is operated normally at not greater than a preset maximum rotation speed. The fan control system has a fan-driving microcontroller to receive an input voltage and a rotation speed signal obtained by detecting the actual rotation speed of the fan motor, adjusting a rotation speed according to the input voltage and the rotation speed signal for driving the fan motor according to the renewed rotation speed. When the rotation speed is lower than a first rotation speed, the rotation speed is in a relation of a first function to the input voltage; when the rotation speed is greater than the first rotation speed, the rotation speed is in a relation of a second function to the input voltage; and a first maximum voltage corresponding to the maximum rotation speed in the relation of the first function is lower than a second maximum voltage corresponding to the maximum rotation speed in the relation of the second function.
In the above-mentioned fan control system, the fan-driving unit can be a fan-driving circuit, and the input signal can be a variable voltage signal. Further, the microcontroller may be programmed to output an alarm when the rotation speed signal is different from a second rotation speed. It is preferable that the first function and the second function are linear functions, and the second function has a slope lower than that of the first function. The above-mentioned fan control system may further have a magnetic induction component, such as a Hall element, for detecting the magnetic field phase of the fan motor in order to output the input signal to the fan-driving microcontroller.